crypto: rockchip - drop redundant crypto_skcipher_ivsize() calls

crypto: rockchip - drop redundant crypto_skcipher_ivsize() calls

The function already initialized the ivsize variable
at the point of declaration, let's use it instead of
calling crypto_skcipher_ivsize() extra couple times.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 57d67c6e8219 ("crypto: rockchip - rework by using crypto_engine")
Signed-off-by: Karina Yankevich <k.yankevich@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>